A typical evaporative emission control system of an automotive vehicle has a vapor collection canister that collects fuel vapors resulting from the volatilization of liquid fuel in the fuel tank so that these vapors do not escape to atmosphere. The collected vapors are periodically purged from the canister to the engine where they entrain with the induction flow for ensuing combustion in combustion chamber space of the engine. Such canister purging occurs under conditions of engine operation that are conducive to purging, consistent with emission laws and regulations applicable to automotive vehicles.
Various forms of canister purge valves have heretofore been proposed and/or used to control the canister purging. Certain forms utilize an electromechanical actuator that controls the opening of a canister purge valve in accordance with an electrical control signal from an engine control computer that manages various functions associated with engine operation. Examples of various canister purge valves are disclosed in commonly assigned patents, such as U.S. Pat. No. 5,199,404, for example.
In certain respects the present invention may be considered as providing further improvements in canister purge valves like those disclosed in U.S. Pat. No. 5,199,404.
One improvement provided by a canister purge flow regulator embodying principles of the present invention is the achievement of better purge control because the effects of detrimental influences on purge control that are attributable to variations in inlet and outlet port differential pressures acting on the purge flow regulator are significantly lessened. Consequently, not only is more accurate purge control attained, but controlled purging can occur at even smaller magnitudes of intake manifold vacuum. Certain prior purge flow regulators were incapable of performing controlled purging at such low intake manifold vacuums.
Another improvement relates to the absence of a bleed path to atmosphere in the inventive canister purge flow regulator; such a bleed was needed in certain prior devices. Generally, elimination of bleed paths in engine system components improves engine idling characteristics, and desirably enables lower engine idle speeds. Thus, absence of a bleed path in the inventive device improves engine operation at low idle speeds, and also eliminates what otherwise might be a potential entrance path for intrusion of minute contaminants in certain operating environments.
Still another improvement relates to the ability of the inventive canister purge flow regulator to respond accurately to an electrical input signal commanding a certain purge flow and to automatically compensate for pressure changes occurring during purge flow that could otherwise significantly alter the commanded purge flow.
The canister of the present invention also incorporates direct electrical actuation, which enables quicker response to any change in input control electrical signals than previously known vacuum operated devices.
Still another improvement provides the potential for reducing certain package size dimensions; such reductions can be significant in facilitating packaging installation in any vehicle where space is at a premium.
The foregoing, as well as further features, advantages, and benefits of the invention, will be seen in the ensuing description and claims which are accompanied by drawings. The drawings disclose a presently preferred embodiment of the invention according to the best mode contemplated at this time in carrying out the invention.